Filter elements are used to remove particulate contaminants from fluids such as air, gases and various liquids required in the operation of engines and equipment or for other uses. Normally, filter elements are made by providing conventional filter media constructions with features required for sealing, fitment, servicing, handling, etc. depending on applications. Filter elements thus made are fitted into filter housings made usually of metal and/or plastic which, in turn, are incorporated into fluid filtration systems.
Three very important performance parameters of a filter element are the pressure drop, particle separation efficiency and contaminant holding capacity. Pressure drop of a filter element is the difference between pressure of fluid at its inlet and that at outlet. Particle separation efficiency is expressed as the percentage of number or weight of contaminant particles removed by the filter element from the incoming fluid. Pressure drop of the filter element increases with usage as more and more contaminant particles carried by the incoming fluid are captured by filter media leading to partial or total blockage of flow channels causing increased restriction to fluid flow. Contaminant holding capacity is the amount of contaminant removed by the filter element before pressure drop reaches the upper limit acceptable in the application. Contaminant holding capacity of the filter element correlates to its life in the field.
In air/gas filtration systems the fluid flow often generates significant level of noise leading to user discomfort. The noise is generated by the turbulence in air/gas flow.
Therefore, it is highly desirable to have air/gas filtration systems with lowest possible flow turbulence.
A good filter element is expected to have minimum pressure drop, maximum particle separation efficiency and maximum contaminant holding capacity. In the case of air/gas filtration it is highly desirable, if a filter element is also suitable for designing a filtration system having lowest possible turbulence thereby achieving low overall pressure drop and noise level. Filter media and the type of filter media construction used to make the filter element largely determine the performance of a filter element.
Filter elements with pleated filter media constructions assembled into cylindrical, conical, panel-type or other forms are well known in prior art for a very long time. In these filter media constructions cross sectional area of inlet flow channel decreases continuously in the flow direction and that of the outlet flow channel increases continuously in the flow direction. The change in cross sectional area creates turbulence in fluid flow leading to higher pressure drop and faster plugging of filter media. As a result, filter elements with pleated filter media constructions give less-than-expected contaminant holding capacity compared to what is expected from filter media performance.
More recently, filter elements with filter media constructions wherein more streamlined fluid flow is achieved by creating multitude of juxtaposed inlet and outlet flow channels, having straight, uniform and identical cross sections in the flow direction, created by pleated or fluted media have been disclosed in prior art. Filter elements with these filter media constructions have been found to offer better performance compared to earlier elements in prior art with pleated filter media constructions assembled into cylindrical, conical, panel-type or other forms. This type of filter elements are known as axial flow filter elements, direct flow filter elements, etc. in prior art.
U.S. Pat. Nos. 4,589,983, 6,946,012, 6,953,124, 7,276,098 and 8,007,572 discloses the use of filter media constructions made of pleated or fluted media. These filter media constructions require pleating or fluting of media to create the multitude of straight, uniform channels needed for achieving streamlined fluid flow.
Normally the filter element manufacturer procures filter media from filter media suppliers and pleats or flutes it using special equipment having rolls with scoring blades or grooves. Pleating or fluting processes have detrimental effects on filter media. It is well understood that pleating or fluting deteriorates original properties of filter media leading to less-than-expected performance especially in contaminant holding capacity. It is also known that the mechanical forces applied by the pleating or fluting equipment on media often damage filter media. High-performance filter media such as laminated, dual or multi-layer media, nano-fibre coated media, micro-glass media, etc. are especially vulnerable in this respect.
It is also known that, in air/gas filtration, even though pleating or fluting allows packaging of more media area in a filter element of given size, filter elements made of pleated or fluted filter media constructions do not give the expected contaminant holding capacity due to restrictions to fluid flow and turbulence caused by geometrical and other constraints in filter media construction and the element.
U.S. Pat. Nos. 3,962,097 and 4,271,025 disclose filter cartridges having layers of filter media coiled around a central support. While this type of filter cartridges may be suitable for liquid filtration having low flow rates, they are not viable for filtration of air or gas streams due to the high restriction to fluid flow and faster plugging of flow paths caused by narrow and/or irregular flow channels.
There is, therefore, a need to develop a filter media construction that overcomes the drawbacks associated with prior art.
Some of the objects of the present disclosure which at least one embodiment is adapted to provide, are described herein below:
It is an object of the present disclosure to provide a filter media construction that is formed without pleating or fluting of filter media.
It is another object of the present disclosure to provide a filter media construction that has uniform axial fluid flow channels for achieving streamlined fluid flow thereby enabling comparatively less pressure drop.
It is still another object of the present disclosure to provide a filter media construction that creates comparatively less turbulence thereby creating comparatively less noise.
It is still another object of the present disclosure to provide a filter media construction wherein flow turbulence is minimized and filter media area usage is maximized in order to achieve substantially lower restriction and higher contaminant holding capacity.
Other objects and advantages of the present disclosure will be more apparent from the following description which is not intended to limit the scope of the present disclosure.